This disclosure relates to an engine exhaust processor, and in particular, to an exhaust processor including a Helmholtz resonator. More particularly, this disclosure relates to an exhaust processor to attenuate noise associated with combustion product produced by the engine.
Noise in a vehicle exhaust system arises from acoustic waves that are generated by the sudden release of exhaust gases from individual cylinders in a vehicle engine. These acoustic waves travel from the engine exhaust manifold through a pipe to a muffler or other resonator on board the vehicle.
In order to dampen these acoustic waves to reduce the sound emitted by a vehicle, resonance chambers are provided in a muffler or other resonator to attenuate the acoustic waves. One type of resonance chamber is a Helmholtz resonator. A resonance chamber absorbs energy from the acoustic waves, which acts to silence somewhat the noise emitted from the muffler. Each resonance chamber is designed to xe2x80x9ctunexe2x80x9d or xe2x80x9csilencexe2x80x9d acoustic waves of a certain frequency.
According to the present disclosure, an exhaust processor includes an acoustic resonator and a resonator controller. The resonator includes a housing providing a static tuning volume and a tuning tube extending into that static tuning volume. The tuning tube receives engine combustion product. An outlet opening is formed in the tuning tube and arranged to lie in the static tuning volume and to place the static tuning volume in acoustic communication with acoustic waves associated with engine combustion product in the tuning tube.
The resonator controller functions to vary the size of the outlet opening so that the tuning frequency of the resonator can be changed by increasing or decreasing the size of the outlet opening. The resonator controller includes an outlet opening size regulator and a regulator operator for moving the regulator over the outlet opening formed in the tuning tube as a function of one or more selected xe2x80x9cengine parametersxe2x80x9d (e.g., engine rpm) to change the size of the outlet opening.
In an illustrative embodiment, the outlet opening is defined by a field of perforations formed in the tuning tube and the resonator controller includes a sleeve that is mounted to slide back and forth on the tuning tube either to xe2x80x9copenxe2x80x9d more perforations in the field (to increase the size of the outlet opening) or to xe2x80x9cclosexe2x80x9d more perforations in the field (to decrease the size of the outlet opening). It is within the scope of this disclosure to use the exhaust processor disclosed herein to attenuate noise associated with combustion product produced by a wide variety of engines (including motor vehicle engines).
In an illustrative embodiment, the resonator controller further includes an engine mode detector that cooperates with the regulator operator to control movement of the sleeve (or other outlet opening size regulator) in a prescribed manner depending upon the xe2x80x9cmode of operationxe2x80x9d of the vehicle engine. Some engines have a variable mode of operating; for example, an eight-cylinder engine could be operated in four-, five-, or six-cylinder mode, depending on the xe2x80x9ccylinder activation or deactivationxe2x80x9d algorithm established in the engine. Engine combustion product is characterized by an xe2x80x9cacoustic signaturexe2x80x9d unique to each mode of operation.
In this embodiment, the engine mode is sensed by the engine mode detector and the regulator operator included in the resonator controller is instructed to move the sleeve relative to the tuning tube to open and close perforations in the field in accordance with a xe2x80x9cpredetermined criteriaxe2x80x9d established in advance for each mode of engine operation and documented in the regulator operator or elsewhere in the exhaust processor. Thus, using the engine mode-sensitive resonator controller disclosed herein, the tuning frequency adjustment system of the acoustic resonator can be changed easily and automatically in a manner best suited to match the acoustic signature associated with each mode of engine operation.
Additional features of the disclosure will become apparent to those skilled in the art upon consideration of the following detailed description of illustrative embodiments exemplifying the best mode of carrying out the disclosure as presently perceived.